#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define int long long
using namespace __gnu_pbds;
using namespace std;
const int mod = 1e9+7;
const int inf = 1e18;
const int maxx = 2e6 + 5;
typedef tree <int, null_type, less_equal <int>, rb_tree_tag, tree_order_statistics_node_update> ordered_multiset;
vector <int> g[maxx], a(maxx);
int n, k, ans = 0;
int dfs(int v, int p) {
int sum = a[v];
for (int u : g[v]) {
if (u == p) {
continue;
}
int j = dfs(u, v);
if (sum + j > k){
ans++;
}
else {
sum += j;
}
}
return sum;
}
void solve() {
cin >> n >> k;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
for (int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
dfs(1, 0);
cout << ans << endl;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
//cin >> t;
while (t--) {
solve();
}
}
